Threats: In view of the substantial socioeconomic benefits, why are so many irreplaceable sites and resources in peril? The degradation of the cultural resource heritage of the United States is the result of a wide range of forces. The simple, enduring processes of wind and water erosion have a significant adverse impact on the integrity of individual resources, and the cataclysmic effect of events such as hurricanes, tornadoes, flooding, and seismic shock can be devastating. Mankind exacerbates the impact of these natural forces of environmental attack by imposing additional threats to culturally significant resources. Threats of man induced resource degradation result not only from neglect and vandalism, but, additionally, from the well-intentioned but inappropriate preservation actions of uninformed administrators, designers, and tradesmen. As a consequence of these cumulative forces, the United States is rapidly losing the tangible, nonrenewable artifacts of its cultural heritage. This lamentable state of affairs is culturally unacceptable and in violation of the spirit (and often the letter) of the federal, state, and local legislation that protects our cultural heritage. Premise: A Basis for Action Preservation Context: Multidimensional and Extensive Threats to Resources